Type of Primer to use on an older trailer

[SDE]

I bought an equiptment trailer. It has an expanded metal floor,which I probably will not try to paint. The frame has old paint and rusty metal. I know I need to clean up the rust. And I know that if I paint over the old paint it may flake off a month from now. I have heard that Epoxy Primer is the best, but I don't like the idea of buying a gallon of expensive primer to do a mediumm size job and then let the prime set in the can for 10 months until I might need it again. Or does it have an indefinite shelf life?
Is there a good alternative? A second best?
Thank you
Steve
 

[Stephen Newell]

The epoxy primer should have a longer shelf life than the catalyst but kept sealed up should last 10 months.

To me the job dictates the type of paint. If you were painting a car or restoring a tractor which takes a great deal of preparation, then I would say you should use the epoxy primer. For a equipment trailer I would just use an alkyd primer and paint. Its not as durable but should last 3-4 years and you can just shoot it again in an afternoon if you don't let it completely fail. A lot depends on the color. Paints with red in it fades a lot faster than other colors. I painted a trailer gray in summer 2009 and it still looks good. Only places where I have damaged it with chains are rusting.
 

[showcrop]

I have often said to not put expensive paint over a quick prep job, but I think that a trailer is a little different in that it gets more abuse than other vehicle paint so adhesion can be a problem. If you plan to tip it up and be sure to get everything loose of with a cup-type knotted wire wheel I would go for Epoxy, otherwise Rustoleum rusty metal primer.